Barrier-film forming apparatus, barrier-film forming method, and barrier-film coated container

ABSTRACT

A barrier-film forming apparatus that forms a barrier film on an inner face of a container having a concave or convex portion as a processing target, including: a dielectric member having a cavity sized to enclose the container, an external electrode covering an outer circumference of the dielectric member, an exhaust unit installed on an end face of the external electrode on a side where a mouth of the container is located, with an insulating member interposed therebetween, and depressurizing inside of the container through an exhaust pipe, an internal electrode inserted from a side of the exhaust pipe and also serving as a gas blowout unit that blows out medium gas for generating a barrier film into the container, and an electric-field applying unit that applies an electric field for generating exhaust between the external electrode and a ground electrode.

BACKGROUND OF THE INVENTION

I. Technical Field

The present invention relates to a barrier-film forming apparatus, abarrier-film forming method, and a barrier-film coated container foruniformly forming a barrier film that provides a gas barrier property toa resin container, for example.

II. Description of the Related Art

Recently, an approach has been adopted to coat an inner face of apolyethylene terephthalate (PET) bottle, which is one type of plasticcontainers, with a film having a high barrier property, for example acarbon film such as diamond-like carbon (DLC) or a silica film, toprevent transmission of external oxygen or transmission of internalcarbon dioxide (for example, from carbonated beverage). Various filmdepositing apparatuses for that purpose are proposed (Japanese PatentApplication Laid-open No. H8-53116, Japanese Patent No. 2788412(Japanese Patent Application Laid-open No. H8-53117), WO2003/101847,Japanese Patent No. 3643813 (Japanese Patent Application Laid-open No.2003-237754), Japanese Patent Application Laid-open No. 2005-247431 andJapanese Patent Application Laid-open No. 2000-230064). Applications ofthis approach are used for medical containers, food containers, and fueltanks to prevent transmission of oxygen, hydrogen, and fuel, ortransmission or absorption of aroma, and the like.

As a film forming apparatus that forms a carbon film on a plasticcontainer using high-frequency plasma chemical vapor deposition (CVD),an apparatus according to Japanese Patent No. 3643813 (Japanese PatentApplication Laid-open No. 2003-237754), which is a basic invention thatachieves coating of inside of a container, will be explained withreference to FIG. 38.

As shown in FIG. 38, a barrier-film forming apparatus forms a film on aninner face of a plastic container 12 having a mouth 11 by dischargeplasma. This barrier-film forming apparatus includes an externalelectrode 13 including an upper external electrode 13-1 and an lowerexternal electrode 13-2 and having a size to enclose an outercircumference of the plastic container 12, and a spacer 25 including adielectric that is interposed at least between the mouth and a shoulderof the container and the external electrode 13 when the plasticcontainer 12 is inserted therein. The barrier-film forming apparatusfurther includes an exhaust pipe 14 attached to an end face of theexternal electrode 13 on the side where the mouth 11 is located, with aninsulating member 26 interposed therebetween, and an internal electrode17 that is inserted into the plastic container from the side of theexhaust pipe 14 into the plastic container 12 within the externalelectrode 13 to be connected to a ground side and has a gas flow channel16 drilled to blow out medium gas 19. The barrier-film forming apparatusfurther includes an exhaust unit (not shown) attached to the exhaustpipe 14, a gas supplier (not shown) that supplies the medium gas 19 tothe internal electrode 17, and a high-frequency power source 18connected to the external electrode 13. Reference numeral 20 denotes agas blowout hole made of an insulating member mounted at a tip of thegas flow channel 16.

The external electrode 13 is installed in a cylindrical earth shield 22having flanges 21 a and 21 b at upper and lower ends, respectively. Thecylindrical earth shield 22 is mounted on an annular base 23. A diskinsulating plate 24 is placed between the annular base 23 and the bottomof the external lower electrode 13-2. The cylindrical insulating member26 is provided at the tip of the gas flow channel 16 of the internalelectrode 17 to prevent local concentration of plasma.

The spacer 25 is fixed by a screw (not shown) threaded therein from theannular insulating member 26 placed on the spacer 25. By inserting andfixing the spacer 25 to an upper part of the external electrode 13 inthis way, the mouth and the shoulder of the plastic container 12 arepositioned in a cavity of the disk spacer 25, and the outercircumference of the plastic container 12 except for the mouth and theshoulder is positioned at the inner face of the external electrode 13,when the plastic container 12 is inserted from the bottom of theexternal electrode 13. The gas exhaust pipe 14 having upper and lowerflanges 31 a and 31 b is placed on the upper flange 21 a of the earthshield 22 and an upper surface of the annular insulating member 26. Acover 32 is attached to the upper flange 31 a of the exhaust pipe 14.

A method of coating the plastic container with a carbon film using theapparatus with the configuration as described above will be explained.

The plastic container 12 is first inserted into the external electrode13, and internal gas is evacuated through the exhaust pipe 14. When aprescribed vacuum is obtained (typical value: 10⁻¹ to 10⁻⁵ Torr), mediumgas G is supplied to the internal electrode 17 at a flow rate of 10 to200 mL/min, for example, and blown out into the plastic container 12through the gas blowout hole 20 of the internal electrode 17, while theevacuation is continued. As the medium gas, an aliphatic hydrocarbon, anaromatic hydrocarbon, an oxygenated hydrocarbon, or a nitrogenoushydrocarbon, such as benzene, toluene, xylene, and cyclohexane is used.A pressure in the plastic container 12 is set at 2×10⁻¹ to 1×10⁻² Torr,for example, depending on balance between an amount of the gas suppliedand an amount of air evacuated. The high-frequency power source 18 thenapplies high-frequency power of 50 to 2000 watts to the externalelectrode 13 through a matching box 36 and a radio-frequency (RF) inputterminal 35.

The application of the high-frequency power to the external electrode 13generates plasma between the external electrode 13 and the internalelectrode 17. At this time, the plastic container 12 is housed withinthe external electrode 13 with almost no space therebetween, and thusthe plasma is generated in the plastic container 12. The medium gas G isdissociated or further ionized by the plasma, and then a film-formingseed for forming a carbon film is generated. This film-forming seed isdeposited on the inner face of the plastic container 12, thereby forminga carbon film. When a predetermined thickness of the carbon film isformed, the application of the high-frequency power is stopped, thesupply of the medium gas is stopped, the remaining gas is evacuated, andnitrogen, noble gas, or air is supplied within the external electrode 13to bring the space back to the atmospheric pressure. The plasticcontainer 12 is then removed from the external electrode 13. This methodtakes two to three seconds to form a carbon film of a thickness of 20 to30 nanometers.

SUMMARY OF INVENTION

However, in this film forming apparatus (Japanese Patent No. 3643813(Japanese Patent Application Laid-open No. 2003-237754)), the shape ofthe hollow space formed by the external electrode 13 and the spacer 25needs to be approximately similar to the shape of the plastic container12 to form a satisfactory film having a high barrier property.

While there is no spacer in Japanese Patent Application Laid-open No.H8-53116 and Japanese Patent No. 2788412 (Japanese Patent ApplicationLaid-open No. H8-53117), the shape of a cavity of an external electrodealso needs to be approximately similar to the shape of a plasticcontainer. In each case, when the container has concave and convexportions (either one of the concave portion and the convex portion, orboth thereof) at its body or the like, the shape of the cavity naturallyneeds to be similar to the shape of the container. However, when theapparatus has a configuration in which the container is insertedlongitudinally, it is difficult to realize such a similar shape.

When the body of the container has relatively few concave and convexportions, a barrier property for practical use can be just obtained evenwhen a slight space is formed at the concave and convex portions.However, because of recent diversification of containers like those seenin container designs for the purpose of reduction in weight andfacilitation in crushing after use, bodies of some containers haveplural concave and convex portions (or recessed portions, concaveportions, or convex portions), or some of the recessed portions (concaveportions) are deep. In such cases, nonuniformity of the formed film isgreatly increased, and therefore the barrier property for practical usecannot be obtained.

A method is conceived of a moving part of the external electrode to beadapted to concave and convex portions of a container after thecontainer is inserted into the external electrode, thereby obtaining asimilar shape. However, such a movable structure needs to be avoided ina high-speed mass production apparatus as much as possible in view ofcost and reliability.

Even when there is no concave or convex and a similar shape can berealized, an electrode completely similar to a container needs to beused, and a clearance therebetween needs to be uniform to obtain ahigher barrier property. However, it is difficult to realize thisbecause of accuracy in molding of the container, accuracy in productionof the external electrode 13 or the spacer 25, or accuracy ininstallation of the container. Therefore, the higher barrier propertycannot be obtained.

In the conventional techniques, there is a proposition (WO2003/101847)that provides an adequate clearance between an external electrode and acontainer. However, when the container has concaves and convexes, it isnecessary to adjust the shape of the clearance from an approximatelysimilar shape to be suited to the concave and convex portions of thecontainer, thereby obtaining a shape that enables the container to beinserted into the clearance and have a high barrier property. Therefore,it is necessary to produce the external electrodes almost entirely toorder to be adapted to diversified shapes of the containers, whichincreases costs and labors. The weight of the external electrode iseasily increased, and thus arrangement of the external electrode orsetting of a movable portion in the configuration of the apparatus isprone to be limited. Therefore, some trouble is caused in an apparatusthat forms a film while a container is transported being inverted, forexample.

In the conventional techniques, there is another proposition (JapanesePatent No. 3643813 (Japanese Patent Application Laid-open No.2003-237754)) of a film forming apparatus having a dielectric spacermainly at positions of the mouth and shoulder of a container. In anotherproposition (Japanese Patent Application Laid-open No. 2005-247431), thedielectric spacer is extended to a lower portion of a container. Thesepropositions are made to adjust film attachment to a small diameter partat the shoulder of a container having no concave and convex at its body,to which an electrode or a spacer having a similar shape can be applied.Accordingly, when the container has concaves and convexes at its body,entire uniformity including film attachment to the body of the containercannot be achieved. That is, no guideline is provided for improvement inuniformity of film distribution, which becomes an issue when a film isformed on a container having concaves and convexes at its body and thelike. This is because voltage to be applied to an inner face of acontainer, which will be explained later, is not uniformized.

In the conventional techniques, there is another proposition (JapanesePatent Application Laid-open No. 2000-230064) of a film formingapparatus having a plastic external cylinder between an electrode and afilm formation target. This plastic external cylinder electricallycontacts the electrode and is a certain distance separated from the filmformation target. This proposition provides no guideline for improvementin uniformity of film distribution either, which becomes the issue infilm formation for a container having concaves and convexes at its bodyand the like. This is also because voltage applied to the inner face ofthe container, which will be explained later, is not uniformized. Theinvention according to Japanese Patent Application Laid-open No.2000-230064 is applied to a film forming apparatus that forms a film onboth of inner and outer faces of the container. A primary object thereofis to prevent heat application to the container, and no guideline isprovided for improvement in film distribution in film formation only onthe inner face.

To sum up, the problems are organized as follows. To form a high-qualitygas barrier thin film, voltage to be applied to the inner face of thecontainer, which will be explained later, needs to be uniformized. Whenan approach from a viewpoint of a structure of the external electrode isadopted, a combination of a space and a dielectric having appropriatesize and composition is provided between the external electrode and thecontainer, thereby optimizing voltage distribution. As described above,there is no conventional technique that achieves such a combination. Ifthis combination can be achieved, various issues other than a high gasbarrier property, specifically including sharing of the externalelectrode with various types of containers, handling of concave andconvex designs of containers, uniform distribution of film thickness,and reduction in weight of the external electrode can be resolved.Therefore, significant effects can be achieved in terms of quality anddevice cost.

The present invention has been achieved to solve the problems abovementioned, and an object of the present invention is to provide abarrier-film forming apparatus, a barrier-film forming method, and abarrier-film coated container capable of forming a uniform film on acontainer having concave and convex surfaces.

According to an aspect of the present invention, in a barrier-filmforming apparatus that forms a barrier film on an inner face of acontainer, voltage to be applied to the inner face of the container ismade approximately uniform by using: a dielectric member installedbetween an external electrode and the container; and a clearance betweenthe external electrode and the container, or a clearance between thedielectric member and the inner face of the container.

Advantageously, in the barrier-film forming apparatus, an internal shapeof the external electrode is tubular or approximately tubular.

According to another aspect of the present invention, a barrier-filmforming apparatus that forms a barrier film on an inner face of acontainer having at least one concave or convex portion as a processingtarget container includes: a dielectric member that has a cavity sizedto enclose the container; an external electrode that covers an outercircumference of the dielectric member; an exhaust unit that isinstalled on an end face of the external electrode on a side where amouth of the container is located, with an insulating member interposedtherebetween, and depressurizes inside of the container through anexhaust pipe; a gas blowout unit that blows out medium gas forgenerating a barrier film, into the container; and an electric-fieldapplying unit that applies an electric field for generating dischargebetween the external electrode and a ground electrode.

Advantageously, in the barrier-film forming apparatus, the gas blowoutunit is grounded, and inserted into the container to serve as aninternal electrode.

Advantageously, in the barrier-film forming apparatus, the cavity sizedto enclose the processing target container matches a space formed by amaximum path line on which the outer circumference of the containerpasses, or has a clearance outside the space.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has a tubular shape having a bottom or a tubular shapesubstantially having a bottom.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has a bottomless tubular shape or a tubular shape having aportion of bottom.

Advantageously, in the barrier-film forming apparatus, a part of theexternal electrode, which faces a space at the concave portion of thecontainer, is covered with the dielectric member.

Advantageously, in the barrier-film forming apparatus, a part of thecavity of the dielectric member, or approximately the entire of thecavity is substantially in contact with the container.

Advantageously, in the barrier-film forming apparatus, the dielectricmember is any one of fluorinated resin, hard vinyl chloride, glass, andceramic, or a combination thereof.

Advantageously, in the barrier-film forming apparatus, a clearancebetween a body of the container and the dielectric member formed whenthe container is placed inside of the dielectric member is designed sothat a difference between a maximum value and a minimum value of a widthof the clearance is equal to or larger than 3 millimeters.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has an approximately uniform thickness.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has a tubular shape or an approximately tubular shape with abottom or without bottom, and an average thickness/a permittivity of thedielectric member is in a range of 0.95 to 3.8.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has a clearance at any one of a shoulder and a mouth of thecontainer, or both thereof.

Advantageously, in the barrier-film forming apparatus, a sum ofconverted distances d_(i)/∈_(i) obtained by dividing a thickness (d_(i))of the dielectric member or a space by a relative permittivity (∈_(i))from an inner surface of the external electrode to the inner face of thecontainer is approximately uniform over the entire container.

Advantageously, in the barrier-film forming apparatus, a material of thedielectric member, thicknesses of the dielectric member and the space,and a shape of the external electrode are combined to make a sum of theconverted distances d_(i)/∈_(i) from an inner surface of the externalelectrode to the inner face of the container approximately uniform oversubstantially the entire container.

Advantageously, in the barrier-film forming apparatus, with respect to asum of converted distances d_(i)/∈_(i) obtained by dividing a thickness(d_(i)) of the dielectric member or a space by a relative permittivity(∈_(i)) at each point of the container surface on a cross section of thecontainer from an inner surface of the external electrode to the innerface of the container, a value obtained by dividing a standard deviationof the sum at each point of the entire container by an average thereofis equal to or lower than 0.75.

According to still another aspect of the present invention, abarrier-film forming apparatus includes: a dielectric member having acavity sized to enclose at least a primary portion of a container as aprocessing target, which cavity matches a space formed by a maximum pathline on which an outer circumference of the container passes, or has aclearance outside the space; an external electrode installed on a sideof an outer circumference of the dielectric member; an exhaust unit thatdepressurizes inside of the container through an exhaust pipe; a gasblowout unit that blows out medium gas for generating a barrier film,into the container; and an electric-field applying unit connected to theexternal electrode to generate discharge in the container, and forming abarrier film on an inner face of the container.

Advantageously, in the barrier-film forming apparatus, the externalelectrode is a ground electrode, and an electrode connected with theelectric-field applying unit is installed in the container or to theexhaust pipe.

Advantageously, in the barrier-film forming apparatus, a part of thedielectric member is in contact with the container, thereby positioningthe container.

Advantageously, in the barrier-film forming apparatus, a part of thedielectric member is in contact with the container, thereby positioningthe container, the part of the dielectric in contact with the containerhas a movable structure; and the movable structure is moved when thecontainer is inserted or removed.

Advantageously, in the barrier-film forming apparatus, a conductiveearth shield sized to enclose the external electrode and being groundedis installed to be insulated from the external electrode.

Advantageously, in the barrier-film forming apparatus, the externalelectrode also serves as a vacuum container.

Advantageously, in the barrier-film forming apparatus, the dielectricmember also serves as a vacuum container.

Advantageously, in the barrier-film forming apparatus, a conductiveearth shield sized to enclose the external electrode and being groundedis installed to be insulated from the external electrode, and the earthshield also serves as a vacuum container.

Advantageously, in the barrier-film forming apparatus, the externalelectrode also serves as a vacuum container, and the external electrodeis in form of a sheet.

Advantageously, in the barrier-film forming apparatus, a conductiveearth shield sized to enclose the external electrode and being groundedis installed to insulated from the external electrode, and an insulatingmember is installed substantially entirely between the externalelectrode and the earth shield.

Advantageously, in the barrier-film forming apparatus, the container asthe processing target has an approximately tubular shape.

Advantageously, in the barrier-film forming apparatus, the container asthe processing target has an approximately tubular shape and has atleast one concave portion.

According to still another aspect of the present invention, abarrier-film forming method of approximately uniformly forming a barrierfilm on an inner face of a container as a processing target uses thebarrier-film forming apparatus described above.

According to still another aspect of the present invention, abarrier-film forming method approximately uniformly forming a barrierfilm on an inner face of a container as a processing target uses thebarrier-film forming apparatus described above. The container as theprocessing target has an approximately tubular shape.

According to still another aspect of the present invention, abarrier-film forming method of approximately uniformly forming a barrierfilm on an inner face of a container as a processing target uses thebarrier-film forming apparatus described above. The container as theprocessing target has an approximately tubular shape and has at leastone concave portion.

According to still another aspect of the present invention, abarrier-film forming method of approximately uniformly forming a barrierfilm on an inner face of a container as a processing target uses thebarrier-film forming apparatus described above. Plural dielectricmembers having various cavity shapes are prepared, one of the dielectricmembers is selected to be suited to a shape or the like of the containeras the processing target, and the barrier film is then formed on thecontainer.

According to still another aspect of the present invention, abarrier-film forming method of approximately uniformly forming a barrierfilm on an inner face of a container as a processing target uses thebarrier-film forming apparatus described above. All or a part of thedielectric member, all or a part of the external electrode, and all or apart of the earth shield are moved together as a unit by a driving unit,and the vacuum container is opened or closed to insert or remove thecontainer.

According to still another aspect of the present invention, in abarrier-film forming method, the barrier-film forming apparatusdescribed above is used, and the container is inserted or removed byneck handling.

Advantageously, in the barrier-film forming apparatus, the dielectricmember has an opening through which the container can be inserted from abottom of the container toward a bottom of the external electrode of atubular shape with a bottom.

According to still another aspect of the present invention, in abarrier-film forming apparatus that forms a barrier film on an innerface of a container, voltage to be applied to the inner face of thecontainer is made approximately uniform by using: a dielectric memberinstalled between an external electrode and the container; and aclearance between the external electrode and the container, or aclearance between the dielectric member and the inner face of thecontainer, a mouth end portion of the external electrode points downwardto orient the container to have a mouth pointing downward, and anexhaust pipe is attached below the end portion of the externalelectrode, with an insulating member interposed therebetween, therebyforming the barrier film on the inner face of the container.

According to still another aspect of the present invention, abarrier-film forming apparatus that forms a barrier film on an innerface of a container having at least one concave or convex portion as aprocessing target container, includes: a dielectric member that has acavity sized to enclose the container; an external electrode that coversan outer circumference of the dielectric member; an exhaust unit that isinstalled on an end face of the external electrode on a side where amouth of the container is located, with an insulating member interposedtherebetween, and depressurizes inside of the container through anexhaust pipe; a gas blowout unit that blows out medium gas forgenerating a barrier film, into the container; and an electric-fieldapplying unit that applies an electric field for generating dischargebetween the external electrode and a ground electrode. A mouth endportion of the external electrode points downward to orient thecontainer to have a mouth pointing downward, and the exhaust pipe isattached below the end portion of the external electrode, with theinsulating member interposed therebetween, thereby forming the barrierfilm on the inner face of the container.

According to still another aspect of the present invention, abarrier-film forming apparatus includes: a dielectric member having acavity sized to enclose at least a primary portion of a container as aprocessing target, which cavity matches a space formed by a maximum passline on which an outer circumference of the container passes, or has aclearance outside the space; an external electrode installed on a sideof an outer circumference of the dielectric member; an exhaust unit thatdepressurizes inside of the container through an exhaust pipe; a gasblowout unit that blows out medium gas for generating a barrier film,into the container; and an electric-field applying unit connected to theexternal electrode to generate discharge in the container. A mouth endportion of the external electrode points downward to orient thecontainer to have a mouth pointing downward, and the exhaust pipe isattached below the end portion of the external electrode, with aninsulating member interposed therebetween, thereby forming a barrierfilm on an inner face of the container.

According to still another aspect of the present invention, in abarrier-film forming method of using the barrier-film forming apparatusdescribed above, the container is vertically inverted, and insertion orremoval of the container into or from the external electrode is thenperformed by neck handling.

According to still another aspect of the present invention, abarrier-film coated container is obtained by approximately uniformlyforming a barrier film on an inner face of a container as a processingtarget by using the barrier-film forming apparatus described above.

According to still another aspect of the present invention, abarrier-film coated container is obtained by using the barrier-filmforming apparatus described above. The container is vertically inverted,and insertion or removal of the container into or from the externalelectrode is then performed by neck handling, thereby forming a barrierfilm on an inner face of the container as a processing target.

According to the present invention, the voltage to be applied to theentire inner face of the container can be uniformized by using thedielectric member installed between the external electrode and thecontainer, and the clearance between the dielectric member and thecontainer. Therefore, a barrier film formed on the inner face of thecontainer can be entirely made uniform, thereby producing the containerwith a high barrier property.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a barrier-film forming apparatusaccording to a first embodiment of the present invention.

FIG. 2 is a principle diagram of film formation in which a dielectricmember is installed.

FIG. 3 is a principle diagram of film formation in which a dielectricmember is installed.

FIG. 4 is a principle diagram of film formation in which a dielectricmember is installed.

FIG. 5 is a schematic diagram of another barrier-film forming apparatusaccording to the first embodiment.

FIG. 6 is a schematic diagram of still another barrier-film formingapparatus according to the first embodiment.

FIG. 7 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 8 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 9 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 10 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 11 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 12 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 13 depicts a relation between a dielectric member and a maximumpath line of a container.

FIG. 14 depicts another relation between a dielectric member and amaximum path line of a container.

FIG. 15 depicts still another relation between a dielectric member and amaximum path line of a container.

FIG. 16 is a schematic diagram of a barrier-film forming apparatusaccording to a second embodiment of the present invention.

FIG. 17 is a schematic diagram of a barrier-film forming apparatusaccording to a third embodiment of the present invention.

FIG. 18 is a schematic diagram of a barrier-film forming apparatusaccording to a fourth embodiment of the present invention.

FIG. 19 is a schematic diagram of a barrier-film forming apparatusaccording to a fifth embodiment of the present invention.

FIG. 20 is a schematic diagram of a barrier-film forming apparatusaccording to a sixth embodiment of the present invention.

FIG. 21 is a cross-sectional view of relevant parts in FIG. 20.

FIG. 22 is a schematic diagram of a barrier-film forming apparatusaccording to a seventh embodiment of the present invention.

FIG. 23 is a schematic diagram of a barrier-film forming apparatusaccording to an eighth embodiment of the present invention.

FIG. 24 is a schematic diagram of a barrier-film forming apparatusaccording to a ninth embodiment of the present invention.

FIG. 25 is a schematic diagram of a barrier-film forming apparatusaccording to a tenth embodiment of the present invention.

FIG. 26 is a cross-sectional view of relevant parts in FIG. 25.

FIG. 27 is a schematic diagram of a barrier-film forming apparatusaccording to an eleventh embodiment of the present invention.

FIG. 28 is a cross-sectional view of relevant parts in FIG. 27.

FIG. 29 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 30 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 31 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 32 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 33 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 34 is a process chart of forming a film on an inner face of acontainer using the barrier-film forming apparatus.

FIG. 35 is a relationship diagram between a barrier improvement factorand a converted distance ratio.

FIG. 36 is a relationship diagram between an average/a standarddeviation of the converted distances G at each position in the containerand the barrier improvement factor BIF.

FIG. 37 is a conceptual diagram of improvement in a barrier property byusing a dielectric member.

FIG. 38 is a schematic diagram of a barrier-film forming apparatusaccording to a conventional technique.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is explained below in detail with reference to theaccompanying drawings. The invention is not limited to the embodiments.In addition, constituent elements in the following embodiments includeelements that readily occur to those skilled in the art or substantiallyequivalent elements.

First Embodiment

A barrier-film forming apparatus according to a first embodiment of thepresent invention will be explained with reference to the accompanyingdrawings.

FIG. 1 is a conceptual diagram of the barrier-film forming apparatusaccording to the present embodiment. The same members as those in thebarrier-film forming apparatus according to the conventional techniqueexplained with reference to FIG. 38 are denoted by like referencenumerals and redundant explanations thereof will be omitted.

As shown in FIG. 1, a barrier-film forming apparatus 10 according to thepresent embodiment forms a barrier film on an inner face of a processingtarget, which is the plastic container (hereinafter, also “container”)12 having at least one concave or convex portion 12 a. The barrier-filmforming apparatus 10 includes a dielectric member 50 that has a cavitysized to enclose at least a major portion of the container 12, theexternal electrode 13 that covers an outer circumference of thedielectric member 50, and an exhaust unit (not shown) that is attachedto an end face of the external electrode 13 on a side where the mouth 11of the container 12 is located, with the insulating member 26 interposedtherebetween, to depressurize the inside of the container 12 through theexhaust pipe 14. The barrier-film forming apparatus 10 further includesthe internal electrode 17 that is inserted from the side of the exhaustpipe 14 and serves also as a gas blowout unit for blowing out the mediumgas 19 for forming a barrier film into the container 12, and anelectric-field applying unit (the high-frequency power source 18 and thematching box 36) that applies an electric field to generate dischargebetween the external electrode 13 and a ground electrode.

According to the present invention, voltage to be applied to the innerface of the container 12 is made approximately uniform in relation ofrelative permittivity ∈₁ inherent in the dielectric member by using thedielectric member 50 installed between the external electrode 13 and thecontainer 12, and a clearance between the dielectric member 50 and thecontainer 12. In this way, a uniform film can be formed on the innerface of the container. Details thereof will be explained later. Thepresent invention has been achieved because it is found thatapproximation using the clearance size and the relative permittivity asdescribed above can be utilized in a practical electrode design, insteadof aiming at uniformity in potential in a narrow sense.

Further, while the external electrode 13 has a cylindrical shape in thepresent embodiment, the present invention is not limited thereto. Forexample, the external electrode 13 can have a prism tubular shape orinclude a constricted part to be adapted to the shape of the containerto be applied. The dielectric member 50 encloses the major portion ofthe container 12, which indicates a body of the container, for example.It indicates that the dielectric member 50 encloses a portionconstituting about more than half of the container surface area, forexample, instead of enclosing only subsidiary portions such as the mouthand the shoulder of the container. While it is assumed that thedielectric member 50 encloses substantially the entire container, casesare assumed in which the major portion does not include special portionssuch as the bottom and a handle of the container, and a portion forwhich the film thickness is to be specially adjusted, which is definedas “enclosing the major portion”.

The external electrode 13 is installed in the earth shield 22 in atubular shape including an earth shield (upper) 22-1 and an earth shield(lower) 22-2 having flanges 22 a and 22 b at upper and lower endsthereof.

The tubular earth shield 22 (the earth shield (upper) 22-1 and the earthshield (lower) 22-2), the external electrode 13 (the external electrode(upper) 13-1 and the external electrode (lower) 13-2), and thedielectric member (a dielectric member (upper) 50-1 and a dielectricmember (lower) 50-2) can be divided into two, i.e., upper and lowerportions, and are removably attached to each other. The disk insulatingplate 24 is located between the annular base 23 and the bottom of theexternal electrode (lower) 13-2.

The exhaust pipe 14 having the upper and lower flanges 31 a and 31 b isformed, and the earth shield 22-1 is hung from the lower flange 31 bthrough the upper flange 22 a. The cover 32 is attached to the upperflange 31 a of the exhaust pipe 14.

The tubular earth shield 22 is made of a conductive material (conductivemember such as aluminum, stainless steel, copper, and brass), and servesboth as an electromagnetic shield for preventing electromagneticradiation and as a high-frequency earth. The earth shield 22 can be madeof a solid material, a mesh, a perforated metal, or the like. The earthshield 22 has the tubular shape, such as a cylindrical shape and aprism, and encloses the entire electrode.

Conductive connectors 41 and vacuum seals (O-rings) 42 are interposed atthe divided portions of the tubular earth shield 22 and the externalelectrode 13, as shown in FIG. 1. The conductive connectors 41 are notalways required when high-frequency conduction is ensured.

The dielectric member (lower) 50-2, the external electrode (lower) 13-2,the insulating plate 24, and the annular base 23 are vertically moved asa unit by a pusher (not shown) with respect to the dielectric member(upper) 50-1 and the external electrode (upper) 13-1, thereby openingand closing the bottom of the external electrode (upper) 13-1. The earthshield (lower) 22-2 is divided together with the annular base 23.

In the present embodiment, the internal electrode 17 as a groundelectrode also serves as a gas blowout unit. However, the presentinvention is not limited thereto, and the ground electrode and the gasblowout unit can be provided separately. It is also possible that nointernal electrode serving as the ground electrode is provided and thatthe exhaust pipe is used as the ground electrode. It is also possiblethat the external electrode serves as the ground electrode and that apower source is connected to the internal electrode, the exhaust pipe,and the like. In sum, it is necessary that that an electric field beapplied between the external electrode enclosing the container and thedielectric member, and another electrode (or other electrodes) togenerate plasma in the container.

The gas blowout unit is inserted into the container from the side of theexhaust pipe. However, the gas blowout unit does not always need to beinserted in the container, and it is only necessary that the medium gasbe supplied inside of the container. Further, it is unnecessary that thegas blowout unit is inserted into the container from the side of theexhaust pipe. When the container has two mouths, for example, the gascan be supplied through one of the mouths, which is not connected to theexhaust pipe, and can be evacuated through the other mouth.

In this embodiment, the high-frequency electric field is used togenerate the discharge. However, an alternating electric field, such asan alternate current (AC), a low frequency wave (LF), a radio frequencywave (RF), a very high frequency wave (VHF), a microwave, and a pulsecan be used, instead of a direct current. In such an electric field, acurrent flows through the dielectric member because of a displacementcurrent even when the dielectric member is located between the externalelectrode and the container. Therefore, the electric field can betransmitted to the inner face of the container, thereby generatingplasma. Among those, it is particularly preferable that the presentinvention be applied to LF, RF, or VHF that can easily form a film of ahigh barrier property and enables the displacement current to easilyflow.

Plastic, glass, or ceramic can be used for the dielectric member 50, forexample. It is only necessary to appropriately form the dielectricmember using one of these or a combination thereof.

Various types of materials can be used for the plastic. Particularly,resin having a low high-frequency loss, and having a high heatresistance, a high flame resistance, and a high mechanical strength ispreferably used. Fluorine resin such as polytetrafluoroethylene,Teflon®, hard vinyl chloride, polycarbonate, PEEK® is preferable. As theceramic, alumina or steatite having a low high-frequency loss, or Macor®having a high machinability is preferably used.

The high-frequency power source 18 that outputs high frequency power isconnected to the external electrode 13 through a cable 34 and the powerfeeding terminal 35. The matching box 36 is connected to the cable 34 tobe interposed between the high-frequency power source 18 and the powerfeeding terminal 35.

The gas blowout hole 20 in a cylindrical shape made of an insulatingmember is provided at the tip of the gas flow channel 16 of the internalelectrode 17, thereby preventing local concentration of plasma. The gasblowout hole 20 can open in a flow direction to be communicated with thegas flow channel 16 of the internal electrode 17 or of a gas blowoutunit that does not serve as the internal electrode, or can be providedon the side wall. The diameter of the internal electrode 17 is equal toor smaller than the inside diameter of the mouth of the plasticcontainer so that the internal electrode 17 can be inserted into theplastic container 12.

The internal electrode 17 is made of a metallic material having a heatresistance, such as tungsten and stainless steel. The internal electrode17 can be made of aluminum. When the surface of the internal electrode17 is smooth, there is a possibility that a carbon film deposited on thesurface of the internal electrode 17 easily peels. Accordingly, thesurface of the internal electrode 17 can be previously sandblasted toincrease roughness of the surface, thereby making the carbon filmdeposited on the surface difficult to peel.

A method of manufacturing a plastic container having an inner facecoated with a carbon film using the barrier-film forming apparatus asdescribed above will be explained. The lower portions that are obtainedby vertically dividing the dielectric member 50, the external electrode13, and the earth shield 22 are lowered as a unit by the pusher (notshown) to open inside. The plastic container 12 is then inserted in theopened dielectric member (lower) 50-2, and then the lower portions aremoved back by the pusher (not shown) to close. This operation is speededup by moving the dielectric member (lower) 50-2, the external electrode(lower) 13-2, the insulating plate 24, the annular base 23, and theearth shield (lower) 22-2 together as a unit. At this time, the plasticcontainer 12 is communicated with the exhaust pipe 14 through the mouth.

Gas inside and outside of the exhaust pipe 14 and the plastic container12 is then evacuated by the exhaust unit (not shown) through the exhaustpipe 14. When a predetermined vacuum is obtained, the medium gas 19 issupplied to the gas flow channel 16 of the internal electrode 17 whilethe evacuation is continued, and the medium gas 19 is blown out from thegas blowout hole 20 of the internal electrode 17 into the plasticcontainer 12 toward the bottom thereof. The medium gas 19 flows from thebottom of the plastic container 12 along the wall toward the mouth 11. Agas pressure in the plastic container 12 has a predetermined valueaccording to balance between the amount of supplied gas and the amountof evacuated gas. It is not necessary that the predetermined gaspressure be always constant, and the gas pressure can be transientlychanged.

The high-frequency power is then supplied from the high-frequency powersource 18 to the external electrode 13 through the matching box 36, thecable 34, and the feeding terminal 35. At this time, voltage is appliedto the inner face of the plastic container due to the high-frequencyvoltage applied between the external electrode 13 (substantially to thecontainer inner face) and the grounded internal electrode 17. Dischargeplasma is generated in the container due to an electric field generatedbetween a plasma sheath edge and the container inner surface. The mediumgas 19 is dissociated due to the discharge plasma, and then a generatedfilm-forming seed is deposited on the inner face of the plasticcontainer 12, thereby forming a carbon film.

When a predetermined film formation time (for example, about one tothree seconds) passes, the carbon film has an approximatelypredetermined thickness. Accordingly, the supply of the high-frequencypower from the high-frequency power source 18 is stopped, the supply ofthe medium gas 19 is stopped, the remaining gas is evacuated, and theevacuation of the gas is stopped. Nitrogen, noble gas, or air is thensupplied into the plastic container 12 through the gas blowout hole 20of the gas flow channel 16 of the internal electrode 17 or through a gassupply valve (not shown) provided on the side of the exhaust pipe, tobring the inside and outside of the plastic container 12 back to theatmospheric pressure. The plastic container having the inner face coatedwith the carbon film is then removed. The plastic container 12 is thenreplaced in the order as described above to start a coating operationfor another plastic container.

In the present embodiment, acetylene is used as the medium gas 19.

The high-frequency power of 13.56 to 100 megahertz from thehigh-frequency power source 18 is used to obtain an output of 100 to1000 watts and a pressure of 0.1 to 1 Torr. The high-frequency power canbe applied continuously or intermittently (in a pulse-like manner). Thefrequency of the high-frequency power to be applied can be set higher(for example, at 60 megahertz) so that a softer carbon film than a DLCfilm can be synthesized. In this way, adhesion to a base material can beenhanced by a synergistic effect with the soft carbon film resultingfrom application of nitrogen or oxygen.

In the film formation according to the present invention, the dielectricmember 50 is provided to cover the major portion of the container 12with a predetermined clearance therebetween. Therefore, no plasmaconcentration occurs, and consequently plasma is generated uniformly,thereby forming a uniform film on the inner face of the container 12having the concave portion 12 a.

That is, in the conventional technique, it is considered that theelectrode needs to closely fit the outer face of the container to obtainhigh barrier. However, in the present invention, the external electrode13 applied with the high frequency is not made to directly fit thecontainer but the dielectric member 50 is placed substantially over theentire surface of the container 12 to apply the uniform voltage to thesubstantially entire inner face of the container 12. Accordingly, thesubstantially entire barrier film formed on the inner face of thecontainer 12 is made homogenous. For example, in the conventionaltechnique, experiences show sufficient improvement of the barrierproperty is not obtained with a simple tubular electrode when concavesand convexes are at least 3 millimeters or larger. Also in such a case,the present invention can achieve a satisfactory barrier property. Theterm “uniform” in the present invention indicates relative uniformity ascompared to a case to which the present invention is not applied, and isnot limited to absolute uniformity.

In the conventional technique, the barrier film has a satisfactory filmquality and a larger thickness at a portion where the electrode is inclose contact with the container, and a higher barrier property isobtained accordingly. However, the film quality and film thickness arereduced at a portion which the external electrode 13 is separated fromthe container, which may lower the entire barrier property of thecontainer.

On the other hand, in the present invention, the external electrode 13has no portion in close contact with the container. Therefore, there isno plasma concentration due to application of voltage to the portionwhere the external electrode 13 is in close contact, and thus a uniformvoltage is applied to the entire container through the dielectric member50. Accordingly, the plasma is generated uniformly, and consequently thefilm quality and film thickness of the container become entirelyuniform, so that a high barrier property can be obtained in the entirecontainer.

Further, in the conventional technique, when the external electrode(metal) partially contacts with a part of the wall of the containerexcept for its bottom due to a defect in centering, for example, thedischarge slightly concentrates on the contact portion, and consequentlythe film formation can be nonuniform. However, in the present invention,the dielectric member 50 is an insulator, and thus a uniform film can beformed also in such a situation.

In the present invention, a barrier film that prevents an odorouscomponent such as an aroma from being adsorbed or absorbed in thecontainer, as well as a barrier film that prevents transmission of gas,liquid, or molecules are also included.

A procedure of forming a film on the container inner face using thebarrier-film forming apparatus having the dielectric member 50 will beexplained in more detail with reference to FIGS. 7 to 12. The container12 having an approximately tubular shape with its cross section beingapproximately square is used as an example.

First, FIG. 7 depicts a state where insertion of the container isstarted. As shown in FIG. 7, the film forming apparatus is divided in avertical axis direction thereof into two, i.e., an upper apparatus 10-1and a lower apparatus 10-2. Insertion by an insertion jig 71 is startedto position the container 12 above the lower apparatus 10-2.

In FIG. 8, the container 12 is inserted into the lower dielectric member50-2 in the vertical axis direction.

A maximum path on which the cross section of the container passes(indicated by a broken line) is referred to here as a container maximumpath line 61. When the container is inserted, the body of the containeris supported by a jig (not shown) to prevent a fall of the container andperform centering thereof.

FIG. 9 depicts a state where the insertion of the container into thelower dielectric member 50-2 is completed, and the bottom of thecontainer 12 is placed within the lower dielectric member 50-2.

FIG. 10 depicts a state where the lower apparatus 10-2 is lifted by thepusher (not shown) to insert the mouth 11 of the container 12 into theupper apparatus 10-1.

FIG. 11 depicts a state where the insertion of the container 12 into thebarrier-film forming apparatus 10 is completed.

FIG. 12 depicts the completed insertion state shown in FIG. 11, in whichthe container 12 is not shown. The container maximum path line 61finally becomes a container visible line excluding the concave portion(depressed portion) 12 a.

In this way, when the dielectric member 50 is positioned outside of thecontainer maximum path line 61 without contacting the container 12, withthe inner face of the dielectric member 50 separated from the container12 with a predetermined clearance 51, the film formed on the containerinner face can be uniformized. In the present embodiment, the containerinner volume is 500 milliliters and the clearance 51 is 1 millimeter.

The dielectric member 50 is installed so that the cavity sized toenclose the container 12 matches a space formed by the container maximumpath line 61 on which the outer circumference of the container 12passes, or has a clearance outside of the space. In this way, uniformfilm formation can be achieved.

It is also possible to prepare a plurality of the dielectric members 50having various cavity shapes to select one of the dielectric members 50to suit the shape of the container 12 as the processing target, and thenform a barrier film on the container. In this way, it is possible tohandle the shape and size of the container and perform uniform filmformation.

A principle indicating that the installation of the dielectric member 50achieves uniformity in film quality and film thickness on the entirecontainer will be explained next with reference to FIGS. 2 to 4 and 35to 37.

In FIG. 2, reference numeral 12 denotes the plastic container, 12 adenotes the concave portion (or the constricted portion), 13 denotes theexternal electrode, 50 denotes the dielectric member, 55 denotes aplasma bulk portion (it is considered that impedance of the bulk portionis low and potential in the bulk portion is almost constant), and 56denotes a plasma sheath portion. Reference “a” denotes a portion (closeportion) where the dielectric member 50 and the container 12 are closeto each other, and b denotes a portion (distant portion) where thedielectric member 50 and the concave portion 12 a of the container 12are distant from each other. Reference d₁ denotes a thickness of thedielectric member 50 at the close portion “a”, d₂ denotes a thickness ofthe dielectric member 50 at the distant portion b, d₃ denotes a distancebetween the dielectric member 50 and the container 12 at the closeportion “a”, d₄ denotes a distance between the dielectric member 50 andthe container 12 at the distant portion b, d₅ denotes a thickness of thecontainer 12 at the close portion “a”, and d₆ denotes a thickness of thecontainer 12 at the distant portion b. In this explanation, thecontainer having an approximately tubular shape with a cross sectionthereof being substantially circular is used as an example.

According to the present invention, the following is assumed. Becausethe dielectric member 50 is installed between the external electrode 13and the container 12, uniformity in distribution of impedance Z from theinner face of the external electrode 13 to the inner surface of thecontainer 12 is improved, and thus uniformity in voltage drop at thisportion is improved. Therefore, uniform voltage is applied to the innersurface of the container 12, thereby improving uniformity in thedischarge in the container 12 and further improving uniformity in thebarrier film formed on the container inner surface. Consequently, thebarrier property of the entire container is enhanced.

The reason why the distribution of the impedance Z from the inner faceof the external electrode to the container inner surface comes close touniformity by installing the dielectric member 50 is considered asfollows.

FIG. 37 is a conceptual diagram of barrier property improvement by thedielectric member as a mechanism. A left drawing in FIG. 37 depicts aconventional apparatus in which the dielectric member 50 is notinstalled, and a right drawing depicts the apparatus according to thepresent invention in which the dielectric member 50 is installed.

In the conventional technique as shown by the left drawing in FIG. 37,RF potential at the plasma sheath edge is assumed to be almost the samein the bottle. Therefore, in the case of the external electrode 13 as asimilar metal electrode, an RF electric field at a portion where thebottle closely contacts the electrode becomes intense and an RF electricfield at a portion where the bottle is separated from the electrodebecomes weak. Consequently, a difference is generated between theportion where the RF electric field is concentrated and the portionwhere the RF electric field is not concentrated.

On the other hand, in the present invention as shown by the rightdrawing in FIG. 37, when the dielectric member 50 of resin or the likeis used, a distance between the external electrode 13 and the sheathedge becomes larger, and thus the concentration of the RF electric fieldis suppressed.

In this case, the resin produces little RF (high-frequency) loss in thedielectric, and thus the RF power supplied to the external electrode 13produces the RF electric field at the sheath portion without loss.Because there is no loss, the RF electric field has the same magnitudeas an average of those in the case where the similar metal electrode isused. This RF electric field generates more uniform plasma.

As a result, the RF electric field becomes uniform and uniform plasma isgenerated, so that a direct-current (DC) bias occurring at the sheathbecomes uniform. Consequently, icon energy becomes uniform and the filmthickness becomes uniform. Because the plasma is uniform, the filmforming seeds are generated uniformly, so that the film thicknessbecomes uniform.

Further, approximately, following arithmetics provide effectiveguidelines.

The electric field that generates discharge in the present invention isan alternating electric field, and can be an electric field having apower supply frequency f of AC, LF, RF, VHF, a microwave, or the like,or including a pulse. In this case, a displacement current can flowthrough the dielectric member installed between the external electrodeand the container inner surface, and the space.

The impedance Z of the dielectric member or the space can be obtained byan expression (1) indicated by a following “Expression 1”.

$\begin{matrix}{\mspace{79mu} \left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack} & \; \\{\mspace{79mu} {{Z = \frac{1}{j\; \omega \; C}}{{{where}\text{:}\mspace{14mu} \omega \mspace{14mu} {denotes}\mspace{14mu} {an}\mspace{14mu} {angular}\mspace{14mu} {frequency}\mspace{14mu} \left( {{or}\mspace{14mu} {power}\mspace{14mu} {supply}\mspace{14mu} {frequency}} \right)},{{and}\mspace{14mu} C\mspace{14mu} {denotes}\mspace{14mu} a\mspace{14mu} {capacitance}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {dielectric}\mspace{14mu} {member}\mspace{14mu} {between}\mspace{14mu} {the}\mspace{14mu} {external}\mspace{14mu} {electrode}\mspace{14mu} {and}\mspace{14mu} {the}\mspace{20mu} {container}},{{or}\mspace{14mu} {the}\mspace{14mu} {space}\mspace{14mu} {\left( {{per}\mspace{14mu} {unit}\mspace{14mu} {area}} \right).}}}}} & (1)\end{matrix}$

Because ω is constant in this case, the impedance Z is determined by thecapacitance C.

For example, the capacitance C in a case where the dielectric member andthe space are arranged in series as shown in FIG. 2 can be obtained byan expression (2) indicated by a following “Expression 2”.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 2} \right\rbrack & \; \\{{C = \frac{1}{\sum\limits_{i}{{ɛ_{i} \cdot ɛ_{0}}\frac{1}{d_{1}}}}}{{{where}\mspace{14mu} i\mspace{14mu} {denotes}\mspace{14mu} {the}\mspace{14mu} {dielectric}\mspace{14mu} {member}\mspace{14mu} {or}\mspace{14mu} {the}\mspace{14mu} {space}},{d\mspace{14mu} {denotes}\mspace{14mu} a\mspace{14mu} {range}\mspace{14mu} ({thickness})\mspace{14mu} {of}\mspace{14mu} {each}\mspace{14mu} {portion}},{ɛ_{1}\mspace{14mu} {denotes}\mspace{20mu} a\mspace{14mu} {relative}\mspace{14mu} {permittivity}},{and}}{ɛ_{0}\mspace{14mu} {denotes}\mspace{14mu} a\mspace{14mu} {permittivity}\mspace{14mu} {in}\mspace{14mu} {vaccum}\mspace{14mu} {\left( {{in}\mspace{14mu} {air}} \right).}}} & (2)\end{matrix}$

A converted distance G can be obtained using the expressions (1) and (2)by an expression (3) indicated by a following “Expression 3”.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 3} \right\rbrack & \; \\{{{Z \propto G} = {\sum\limits_{i}\frac{d_{i}}{ɛ_{i}}}}{{where}\mspace{14mu} G\mspace{14mu} {denotes}\mspace{14mu} {an}\mspace{14mu} {converted}\mspace{14mu} {{distance}.}}} & (3)\end{matrix}$

That is, the converted distance G is the sum of the ranges (thicknesses)d₁ of respective portions divided by the relative permittivity ∈₁. Therelative permittivity ∈ of the space is 1.

The converted distance G corresponds to a range (thickness) of anelectrical space when a dielectric is entirely replaced by a space.According to this definition, uniformity of the impedance Z from theinner face of the external electrode to the inner surface of thecontainer is represented by uniformity of the converted distance G, thatis, a ratio of the converted distances G at respective positions of thecontainer.

Therefore, when the ratio of the converted distances G is smaller, theimpedance Z from the inner face of the external electrode to the innersurface of the container becomes more uniform, and thus the barrier filmformed on the inner surface of the container becomes approximatelyuniform. Accordingly, the barrier property is improved.

The ratio of the converted distances G in the conventional technique (inthe case where no dielectric is provided) is explained first as acomparative example.

To simplify the explanation, only two points, which are both ends of thespectrum (the close portion “a” and the distant portion b) as shown inFIG. 2 are considered, and the wall (thickness) of the container 12 isignored because it is sufficiently thin (d₅=d₆=0).

In FIG. 2, when the dielectric member 50 is replaced by metal, forexample, the metal constitutes a part of the external electrode, whichbecomes a simulant of the conventional technique. That is, theconventional external electrode having a cavity along the containermaximum path line is obtained.

In this case, d₂=d₂=0 and the relative permittivity ∈ of the space is 1.Therefore, the converted distance Gmin at the close portion “a” is d₃,and the converted distance Gmax at the distant portion b is d₄.

Accordingly, the ratio Gmax/Gmin of the converted distances is d₄/d₃.

A ratio of the converted distances G in the present invention (in thecase where the dielectric member is provided) will be explained.

In FIG. 2, the dielectric member 50 is made of resin (“Teflon®”), forexample.

In this case, the converted distance Gmin at the close portion “a” isd₃+d₁/∈_(D), and the converted distance Gmax at the distant portion b isd₄+d₂/∈_(D).

Here, ∈_(D) denotes a relative permittivity of the dielectric.

Because d₂=d₂ in the example shown in FIG. 2, the ratio Gmax/Gminbetween the converted distances G is (d₄+d₁/∈_(D))/(d₃+d₁/∈_(D)).

Because d₄>d₃ and d₁/∈_(D)<0, the ratio Gmax/Gmin between the converteddistances G in the present invention is smaller than that of thecomparative example (conventional technique) described above, whichindicates that the uniformity is improved (uniformity is obtained).

In the configuration as shown in FIG. 2, the dielectric member and theexternal electrode are installed to enclose the entire container.However, a relative permittivity (∈_(i)) of a dielectric member 50B of aportion facing the portion b at which the clearance between thecontainer 12 and the dielectric member is large can be made differentfrom a relative permittivity (∈_(i)) of a remaining dielectric member50A, thereby changing the converted distances, as shown in FIG. 3. Thisfurther contributes to the uniformity of the voltage applied to theinner face of the container.

It is also possible that the dielectric member 50 is installed to covera position of the electrode facing the portion b at which the spacebetween the container 12 and the electrode is large and a space isformed at the remaining portion, thereby changing the converteddistances, as shown in FIG. 4. This contributes to substantialuniformity of the voltage applied to the inner face of the container.Although not shown, a thin dielectric member can be attached to a metalsurface of the external electrode not to expose the metal surface in thespace.

Specific explanations will be given below with reference to actualcomparison and experiment results shown in “Table 1” and “Table 2”.

Also in the following discussion, the thicknesses d₅ and d₆ of thecontainer are ignored (d₅=d₆=0) because the wall of the container issufficiently thin.

In comparative examples 1 to 4 shown in Table 1, the depth of theconcave portion (constrained portion) 12 a of the container was variedin the conventional technique (replacing the dielectric member withmetal) to check the ratio Gmax/Gmin of the converted distances G at theclose portion “a” and the distant portion b, and a barrier improvementfactor (BIF).

The barrier improvement factor was measured by using a common MOCONmethod.

TABLE 1 Comparative example Experiment number Symbol 1 2 3 4 Outerchamber configuration Metal nesting Outer chamber shape Shape alongcontainer maximum path line Bottle constriction depth 0 mm 5 mm 10 mm 15mm Close portion Design clearance (mm) d₃ 0.75 0.75 0.75 0.75 Dielectricthickness (mm) d₁ 0 0 0 0 Dielectric relative ε₁ 1 1 1 1 permittivityConverted distance G Gmin 0.75 0.75 0.75 0.75 Distant portion Designclearance (mm) d₄ 0.75 0.75 0.75 0.75 Constriction range (mm) 0 5 10 15Dielectric thickness (mm) d₂ 0 0 0 0 Dielectric relative ε₂ 1 1 1 1permittivity Effective distance G Gmax 0.75 5.75 10.75 15.75 RatioGmax/Gmin of effective 1 8 14 21 distances G Barrier improvement factor26.3 10.2 7.0 6.5 BIF (times) O₂ passage amount 12.4 32.0 46.0 51.0(cc/pkg/day)

TABLE 2 Experiment Example number Symbol 1 2 3 4 5 6 7 8 9 10 11 Outerchamber Teflon thickness Teflon thickness Teflon Teflon Teflon TeflonVinyl configuration 2 mm 4 mm thick- thick- thick- thick- chloride nessness ness ness thickness 4 mm 8 mm 2 mm 4 mm 4 mm Outer chamber Shapealong container maximum path line Cylindrical shape with bottom shapeBottle 0 mm 5 mm 10 mm 0 mm 5 mm 10 mm 10 mm constriction depth Closeportion Design d₃ 1 1 1 1 1 1 1 1 3 3 3 clearance (mm) Dielectric d₁ 2 22 4 4 4 4 8 2 4 4 thickness (mm) Dielectric ε₁ 2.1 2.1 2.1 2.1 2.1 2.12.1 2.1 2.1 2.1 3.1 relative permittivity Converted Gmin 1.95 1.95 1.952.90 2.90 2.90 2.90 4.81 3.95 4.90 4.29 distance G Distant portionDesign d₄ 1 1 1 1 1 1 1 1 3 3 3 clearance (mm) Constriction 0 5 10 0 510 20 20 20 20 20 range (mm) Dielectric d₂ 2 2 2 4 4 4 4 8 2 4 6thickness (mm) Dielectric ε₂ 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 3.1relative permittivity Effective Gmax 1.95 6.95 11.95 2.95 7.90 12.9022.90 24.81 2.95 24.90 24.29 distance G Ratio Gmax/Gmin 1 4 6 1 3 4 8 56 5 6 of effective distances G Barrier 33.0 19.5 22.4 35.0 29.9 25.4 9.312.7 11.2 12.7 18.0 improvement factor BIF (times) O₂ passage 12.0 20.017.0 11.3 13.0 15.0 41.0 30.0 34.0 30.0 22.0 amount (cc/pkg/day)

Results of the experiments show that when the concave portion(constricted portion) 12 a has a larger depth, the ratio Gmax/Gmin ofthe converted distances G becomes larger, and the barrier improvementfactor is greatly reduced.

Next, in examples 1 to 3, the dielectric member (Teflon®) 50 has aninner cavity with a shape along the container maximum path line, and hasa thickness of 2 millimeters. With respect to the same depth of theconcave portion (constricted portion) 12 a, the ratios Gmax/Gmin of theconverted distances G in these examples become smaller than those in thecomparative examples. Consequently, the barrier improvement factors aregreatly enhanced.

In examples 4 to 6, the thickness of the dielectric member (“Teflon®”)50 is increased and set at 4 millimeters. Accordingly, the ratiosGmax/Gmin of the converted distances G are further reduced, and thebarrier improvement factors are further enhanced.

In examples 7 to 11, the dielectric member has a tubular shape having abottom with the cavity in the dielectric member being cylindrical, andan projection at the container shoulder as shown in FIG. 2 is notprovided. Accordingly, unlike the examples 1 to 6, the shoulder isseparated from the electrode farther than at the container constrictedportion. That is, the distant portion b is situated at the shoulder, andthere is a large space at the shoulder. Accordingly, while the barrierproperties are relatively lower than those in the examples 1 to 6, thebarrier properties are improved so much as compared to the conventionalcase in which no dielectric member is provided.

In the examples 7 and 8, the dielectric members (“Teflon®”) 50 havedifferent thicknesses (4 millimeters and 8 millimeters). In the examples9 and 10, the thickness of the dielectric member is 4 millimeters, andthe clearance d3 is changed. In the example 11, the material of thedielectric member is changed to a hard vinyl chloride.

Also in these examples, there was a tendency that the barrierimprovement factor is further enhanced when the ratio Gmax/Gmin of theconverted distances G is smaller.

Therefore, it was found that the average thickness/the relativepermittivity of the dielectric member had preferably a range of 2 mm/2.1to 8 mm/2.1=0.95 to 3.80.

FIG. 35 collectively depicts these data in terms of the ratio Gmax/Gminof the converted distances G and the barrier improvement factor.

An approximate expression of all the data is obtained from FIG. 35 asthe following expression (4).

y=36.03x ^(−0.539)  (4)

Generally, a coated barrier container is required to have a barrierproperty ten or more times, or preferably fifteen or more times higherthan that of the original container. By using the approximate expression(4), it was found that the ratio Gmax/Gmin between the maximum converteddistance and the minimum converted distance should be equal to or largerthan 1 and equal to or smaller than 11 to have the barrier property tenor more times higher, and be equal to or large than 1 and equal to orsmaller than 5 to have the barrier property fifteen or more timeshigher. The ratio of the converted distances is a nondimensional number(value with no unit) because it is obtained by dividing a distance by adistance.

These data come true in the case of a typical vertically-long containerhaving a circular cross section (such as a PET bottle). When thecontainer has a special shape, a similar tendency is indicated while theabsolute value can be slightly different.

As described above, the improvement in the barrier property due to theinstallation of the dielectric member 50 is effective also when thebarrier-film forming apparatus including the external electrode and thedielectric member having the same shape is used for containers ofdifferent shapes.

That is, even when the clearance between the container and the cavity ofthe dielectric member is increased because of the different containershapes, influence on the ratio Gmax/Gmin of the converted distances canbe reduced. The tubular shapes with bottoms in the examples 7 to 11 aresuitable for such an application because they can be used regardless ofthe container shapes when the diameter and the length are acceptable.

This eliminates the need to prepare the external electrodes or thedielectric members of all shapes similar to various types of containers.Therefore, a great advantage is achieved because type change is notrequired or it is only necessary to select one of dielectric members ofseveral shapes, which is most suited to each bottle, and use theselected one for manufacturing.

In this application, the clearance can be greatly increased.

In the present invention, the metallic surface of the external electrodedoes not directly face a large space between the container and theexternal electrode because of the installation of the dielectric member.Therefore, it is possible to prevent generation of unwanted discharge inthe space.

The following was also found from FIG. 35. It is desirable that, as amethod for applying uniform voltage to the inner face of the containerand obtaining a high barrier property, the sum of d/∈ with respect tothe minimum distance from the inner surface of the container to thedielectric member 50 or the external electrode 13 is obtained, and theratio Gmax/Gmin of the converted distances is set to be equal to orsmaller than 11 (corresponding to the barrier property ten timeshigher), preferably equal to or smaller than 5 (corresponding to thebarrier property fifteen times higher), and more preferably equal to orsmaller than 3.2 (corresponding to the barrier property twenty timeshigher).

Ideally, it is desirable that the sum is obtained by integration at eachpoint of the container. As an alternative method, it is possible to setpoints at intervals of 0.5 centimeter, for example, from the mouth tipof the container to the bottom of the container, and obtain the sum ateach point. At this time, it is possible to set container surface pointson the cross section of the container passing through the center of thecontainer, for example.

As another method, it is possible to obtain a standard deviation/anaverage of the sum of d/∈ at the respective container surface positionsby using the examples 1 to 11 and the comparative examples 1 to 3. Atthis time, these container surface positions can be set on the crosssection surface of the container. In this case, it is possible that thestandard deviation/the average of the sum of d/∈ at the respectivecontainer surface positions is equal to or lower than 0.75(corresponding to the barrier property ten times higher), preferablyequal to or lower than 0.66 (corresponding to the barrier propertyfifteen times higher), and more preferably equal to or lower than 0.57(corresponding to the barrier property twenty times higher). Thecomparative example 4 is eliminated because the constriction depth is 15millimeters.

These results are shown in Table 3 and FIG. 36.

TABLE 3 Comparative Example example 1 2 3 4 5 6 7 8 9 10 11 1 2 3STD/AVE 0.45 0.48 0.66 0.37 0.39 0.55 0.7 0.56 0.62 0.56 0.75 0.58 0.60.82 BIF 33 19.5 22.4 35 29.9 25.4 9.3 12.7 11.2 12.7 18 26.3 10.2 7 OTR12 20 17 11.3 13 15 41 30 34 30 22 12.4 32 46

The present invention can provide uniform film formation over the entirecontainer because the voltage applied to the container inner face ismade approximately uniform by using the dielectric member locatedbetween the external electrode and the container, and the clearancebetween the external electrode and the container or the clearancebetween the dielectric member and the container inner face.

On the other hand, when a similar electrode is used like in theconventional technique (Japanese Patent Application Laid-open No.H8-53116 or Japanese Patent No. 2788412 (Japanese Patent ApplicationLaid-open No. H8-53117)), it is practically difficult to obtain acompletely similar shape due to the accuracy in molding of thecontainer, the accuracy in production of the external electrode 13 orthe spacer 25, or the accuracy in installation of the container.Therefore, a higher barrier property cannot be obtained. The externalelectrode and the internal electrode are quite close to each other at aportion having a quite small diameter from the mouth to the shoulder ofthe container. Accordingly, the approximate theory as described abovecannot be applied, and the electric field on the inner surface of thecontainer becomes quite large even when the voltage applied to thecontainer inner surface at that portion is the same as that at theremaining portion. Therefore, the discharge becomes high, the filmforming rate is increased, and thus a uniform thin film cannot beformed.

It is estimated that the approximate theory holds true at portions inwhich the diameter of the container is not significantly small and theplasma potential can be assumed to be almost the same, and does not holdtrue at portions having small diameters such as the mouth and theshoulder.

There is another proposition (WO2003/101847) of providing a clearancebetween the external electrode and the container mainly for the purposeof reducing a large electric field from the mouth to the shoulder of thecontainer. When a container having concaves and convexes is a target,the shape of the clearance needs to be adjusted from an approximatesimilar shape to be suited to the concave and convex portions, therebyobtaining a shape that enables the container to be inserted into theclearance and have a high barrier property. Therefore, the externalelectrodes need to be produced almost entirely to order to be suited todiversified container shapes, which increases cost and labor. Further,because the clearance is increased, the plasma is easily generated inthe clearance. Accordingly, the clearance width has a limitation, theeffect of applying uniform voltage is restrictive, and thus it isdifficult to obtain a uniform thin film on the entire container. Inaddition, the problem of the voltage distribution due to the accuracy inmolding of the container, the accuracy in production of the externalelectrode 13 or the spacer 25, or the accuracy in installation of thecontainer cannot be resolved, and thus a high barrier property cannot beobtained. Variations in the improvement of the barrier property arelikely to increase.

Further, there are the proposition (Japanese Patent No. 3643813(Japanese Patent Application Laid-open No. 2003-237754)) of providing adielectric spacer mainly at positions corresponding to the mouth and theshoulder of the container, and the proposition (Japanese PatentApplication Laid-open No. 2005-247431) of extending the dielectricspacer to the lower portion of the container. These propositions alsohave a primary object to reduce a large electric field from the mouth tothe shoulder of the container. Therefore, while these propositions canadjust the film attachment to a small-diameter portion of the shoulderof a container that has no concave and convex at the body and to whichan electrode or a spacer having a similar shape can be applied, thesepropositions cannot achieve entire uniformity including the filmattachment to the body of the container having concaves and convexes atthe body. These propositions cannot resolve the problem resulting fromthe accuracy in molding of the container, the accuracy in production ofthe external electrode 13 or the spacer 25, or the accuracy ininstallation of the container, either. Accordingly, a high barrierproperty cannot be obtained.

In the conventional techniques, there is the proposition (JapanesePatent Application Laid-open No. 2000-230064) of the film formingapparatus in which the plastic external cylinder that electricallycontacts the electrode and is a certain distance separated from the filmformation target is provided between the electrode and the filmformation target. However, this apparatus forms a film on both of innerand outer faces of the container and has a primary object to preventheat application to the container. Accordingly, this proposition iscompletely different from the present invention aimed at forming a filmonly on an inner face of the container and having an object to improvefilm distribution by uniformizing the voltage distribution. Therefore,this proposition provides no guideline for improving the reduced barrierproperty resulting from the uniformity in the film distribution or thevarious accuracies, which becomes an issue in forming a film on thecontainer having concaves and convexes at the body or the like.

The foregoing is the study with respect to the cross section in adirection horizontal to the direction of the insertion of the containerinto the external electrode. A cross sectional direction perpendicularto the insertion axis of the container will be studied below.

FIGS. 13 to 15 depict the containers 12 having circular and square crosssections, and the like.

As shown in FIG. 13, when the container 12 has a substantially circularcross section, the converted distances G are substantially uniform atany point, and thus there is no influence on the barrier property.

FIG. 14 depicts a case where a container (square) having an unfixedradius such as a polygon is inserted to be coated.

Also in this case, like in the case of the horizontal cross section, theratio Gmax/Gmin of the converted distances G is(d₄+d₁/∈_(D))/(d₃+d₁/∈_(D)) and is smaller than that in the case whereno dielectric member is provided, and therefore an enhanced barrierproperty is obtained.

Only by providing one dielectric member having such a shape, the presentinvention can handle containers from a circular container to varioustypes of square containers.

Unlike a dielectric member having a square cavity as shown in FIG. 15,the container can be inserted into the apparatus at a free angle withoutthe need of adjusting the angle in the axial direction of the container.Therefore, an inserting device can be simplified.

Finally, FIG. 15 depicts a case of a dielectric member having a squarecavity similar to the outer shape of the container. In this case,because a part of d₄ is replaced by d₂ of the relative permittivity∈_(D), the ratio Gmax/Gmin (=(d₄+d₂/∈_(D))/(d₃+d₁/∈_(D))) of theconverted distances G becomes smaller than (b), and thus the barrierproperty is enhanced. In this case, a dielectric having a larger ∈_(D),for example alumina, is more preferably used as the dielectric memberbecause the converted distances G become smaller.

Although not shown, the external electrode can have a prism tubularshape.

A polygonal dielectric member can be used for a polygonal containerbased on the same concept as for the square shape.

The dielectric member 50 preferably encloses at least the body of thecontainer 12.

The dielectric member 50 can be of a tubular shape with a bottom orapproximately a tubular shape with a bottom. Alternatively, thedielectric member 50 can be of a tubular shape without bottom or atubular shape partially having a bottom.

A part of the external electrode 13 facing the space of the concaveportion 12 a of the container 12 can be covered by the dielectric member50.

A part of the cavity of the dielectric member 50 or approximately theentire cavity can be in approximate contact with the container.

A part of the dielectric member facing the concave portion 12 a of thecontainer 12 can have a different relative permittivity ∈.

The dielectric member can have a convex shape to be suited to the shapeof the concave portion.

Dielectric members having different relative permittivities ∈_(i) can belaminated.

In this way, the sum of the converted distances d_(i)/∈_(i) from theinner surface of the external electrode to the inner surface of thecontainer is made approximately uniform over the approximately entirecontainer by variously setting the material of the dielectric member andthe thickness of the space, thereby achieving uniformity in the formedfilm.

The conventional techniques have the problem in that even for thecontainer 12 having no concave portion 12 a, it is practically difficultto form the external electrode and the like in a shape completelysimilar to the container due to the accuracy in molding of thecontainer, the accuracy in production of the external electrode 13 orthe space 25, or the accuracy in installation of the container, andtherefore a high barrier property cannot be obtained. However, in thepresent invention, the uniformity in the voltage applied to the innerface of the container can be obtained by the dielectric member, and thusthe uniform film can be formed on the inner face of the container, whichenhances the barrier property.

Preferably, the container has an approximately tubular shape. Thecontainer of a tubular shape indicates a container having a small mouthand a large body and being vertically long, and its side has acylindrical shape or a prism tubular shape with panels. Containers withand without concave and convex portions are included.

FIG. 5 depicts a barrier-film forming apparatus including the dielectricmembers at positions facing the concave portions of the container, asanother example of the present embodiment. Also with this apparatus, thevoltage can be made approximately uniform by using the dielectric member50 installed between the external electrode and the container, and aclearance d₇ between the external electrode 13 and the container 12 orthe clearance d₄ between the dielectric member 50 and the container 12,which enables to form a uniform film over the entire container, asexplained with reference to FIG. 4. When the metallic electrode isexposed to the relatively large clearance as in this example, abnormaldischarge may be generated. Accordingly, at least a thin dielectric canbe provided on the surface of the external electrode to suppress theabnormal discharge.

FIG. 6 depicts the container 12 having an upper end largely opening likea cup. When a barrier film is to be formed in the container like a cup,the voltage can be made approximately uniform by using the dielectricmember 50 installed between the external electrode and the container,and the clearance d₇ between the external electrode 13 and the container12 or the clearance d₄ between the dielectric member 50 and thecontainer 12, thereby enabling to form a uniform film over the entirecontainer.

Second Embodiment

FIG. 16 is a schematic diagram of a barrier-film forming apparatusaccording to another embodiment of the present invention.

As shown in FIG. 16, the shape of the container 12 is changed to have acircular cross section, and the clearance 51 is at least 3 millimeters.

According to the present embodiment, even when the clearance 51 betweenthe dielectric member 50 and the container 12 is increased, a uniformand satisfactory film (having the BIF fifteen times higher or a higherBIF) can be formed on the inner face of the container.

Third Embodiment

FIG. 17 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 17, the shape of the container 12 is changed to have acircular cross section, and the clearance 51 is at least 1 millimeter.

A dielectric member 62 of a convex shape corresponding to a concaveportion 12 b at the bottom of the container is further provided.

According to the present embodiment, uniform film formation can beachieved also at the concave portion 12 b at the bottom of thecontainer, as well as the concave portion 12 a at the body of thecontainer.

Fourth Embodiment

FIG. 18 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 18, in the present embodiment, an upper projection 50-3of the dielectric member is provided to the apparatus shown in FIG. 17to enhance the electric field at the shoulder of the container 12. Theshape of the projection does not need to completely fit the containershape to achieve the effect of the present invention, and the projectioncan have a shape with a margin that enables to accept various shouldershapes of the container. The upper projection 50-3 also performs acentering function with respect to the central axis of the containermouth 11. It is assumed in the present invention that the approximatelytubular shape of the dielectric member also includes shapes that includea portion not completely fitting the container but can accept variousshapes of the containers.

According to the present embodiment, a uniform film can be formed alsoat the container shoulder, as well as at the container body.

Fifth Embodiment

FIG. 19 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 19, a lower projection 50-4 of the dielectric member isprovided to the apparatus as shown in FIG. 18 to further enhance theelectric field on the lateral face at the bottom of the container 12.The lower projection 50-4 also performs a centering function withrespect to the central axis of the container mouth 11.

The lower projection does not need to have a shape completely fit thecontainer shape, and can have a shape with a margin that enables toaccept various shapes of the bottom of the container. It is alsopossible to bring the lower projection into contact with the lateralface at the bottom of the container, thereby preventing fall of thecontainer 12.

Sixth Embodiment

FIGS. 20 and 21 are schematic diagrams of a barrier-film formingapparatus according to still another embodiment of the presentinvention.

As shown in FIGS. 20 and 21, a movable projection 50-5 of the dielectricmember, which can freely move toward the central axis, is furtherprovided to the apparatus as shown in FIG. 18 at the bottom of thecontainer 12. The movable projection 50-5 can be a unit that is easilytaken out, such as a spring mechanism and other similar configurations.The movable projection 50-5 centers the container 12 and prevents thecontainer 12 from falling, when the container 12 is inserted. Themovable projection 50-5 also has an effect of enhancing the electricfield of the lateral surface of the container 12.

Seventh Embodiment

FIG. 22 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 22, a conical external electrode 13-3 is providedinside the upper external electrode 13-1 to assume various shouldershapes of the container 12. To obtain a higher barrier property, theconical external electrode 13-3 can be further adapted to have a similarshape to a specific container, or have an approximately similar shape tosome containers.

According to the present embodiment, by installing the conical externalelectrode 13-3, the thickness of the dielectric member at the shoulderof the container 12 becomes relatively approximately uniform, and theupper electric field of the container 12 becomes more uniform.Consequently, a more uniform film can be formed.

Eighth Embodiment

FIG. 23 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 23, in the present embodiment, the dielectric memberforms a vacuum chamber, and a sheet-like metallic sheet 80 is attachedaround the dielectric member as the external electrode.

Preferably, the metallic sheet 80 is aluminum or stainless steel, forexample, and its thickness is equal to or larger than about 50micrometers, corresponding to a high-frequency skin effect. Thethickness has no upper limit and can be about 5 millimeters, forexample.

The sheet according to the present invention is not limited to a commonmetallic sheet, and can be a plate material like a can, a see-throughmetal such as a punched board and a net, or a thin film such as plating.

Further, contacts are preferably provided around the metallic sheet 80to ensure electrical contact between upper and lower portions thereof.

In the present embodiment, in addition to the effects of the presentinvention described above, effects such as reduction in weight of theelectrode configuration, improvement of flexibility in the design shape,reduction in production costs due to facilitation of mechanicalprocessing, internal visualization by using a see-through metal and atransparent resin member (for example, transparent hard vinyl chloride),and facilitation in adjustment of the plasma distribution due to theinternal visualization can be obtained. The earth shield is also asee-through metal.

Ninth Embodiment

FIG. 24 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention.

As shown in FIG. 24, the earth shield 22 as an external earth shieldforms a vacuum chamber. A dielectric member is embedded between theearth shield 22 and the metallic sheet 80 to reduce an empty space andimprove the sealing property. The space can be left.

In the present embodiment, the special effects achieved in the eighthembodiment are further increased, and breakdown in the empty space canbe suppressed.

When a metallic sheet is used for the earth shield like the externalelectrode 80, the reduction in weight and cost can be realized.

Tenth Embodiment

FIG. 25 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention. FIG. 26is a cross-sectional view of relevant parts in FIG. 25.

As shown in FIGS. 25 and 26, the dielectric member 50 in the presentembodiment is made of foam having numerous voids 52. The presence of thevoids 52 substantially reduces the relative permittivity ∈_(D), andreduces the ratio of the converted distances.

Eleventh Embodiment

FIG. 27 is a schematic diagram of a barrier-film forming apparatusaccording to still another embodiment of the present invention. FIG. 28is a cross-sectional view of relevant parts in FIG. 27.

As show in FIGS. 27 and 28, a dielectric member having numerous slits 53is installed in the present embodiment. The presence of the slits 53substantially reduces the relative permittivity ∈_(D) and reduce theratio of the converted distances.

Twelfth Embodiment

FIGS. 29 to 31 are schematic process charts of a barrier-film formingapparatus according to still another embodiment of the presentinvention.

As shown in FIG. 29, the dielectric member 50 having a sufficient spaceto assume the container 12 of various sizes is installed inside theexternal electrode 13, and the container 12 is inserted through theupper opening by means of the insertion jig 71.

As shown in FIG. 30, the mouth 11 of the container 12 is then held by amovable jig 90 that can move in the vertical axis direction from theside of the exhaust pipe 14, and a mouth holding jig 91 mounted on thetip of the movable jip 90, thereby fixing the container 12.

The external electrode including the dielectric member 50 and the earthshield 22 are then lifted to receive the container 12, as shown in FIG.31.

According to the present embodiment, because the mouth 11 of thecontainer 12 (particularly the PET bottle) generally has anapproximately standardized shape, the container of any shape can beprocessed by one type handling device as long as the handling deviceperforms neck handling to hold the mouth. Therefore, there is no need tochange types of the holding jig for the body, which is required when thebottom of the container is inserted in the conventional techniques or inthe above embodiments.

Accordingly, various containers can be installed in the barrier-filmforming apparatus by a simple operation of neck handling when thecontainers can be inserted into the dielectric member 50. In addition,the presence of the dielectric member 50 enables to form a uniform filmover the inner surface of the container.

In the present embodiment, by changing a part of the dielectric memberof a tubular shape, for example at the mouth or the shoulder of thecontainer, to a shape approximate (not completely similar) to thecontainer shape, the dielectric member can have a shape that can acceptvarious types of containers. The approximately tubular shape accordingto the present invention also includes such a shape.

Thirteenth Embodiment

FIGS. 32 to 34 are schematic diagrams of a barrier-film formingapparatus according to still another embodiment of the presentinvention.

The barrier-film forming apparatus according to the present embodimenthas a configuration obtained by vertically inverting the barrier-filmforming apparatus as shown in FIGS. 29 to 31, and thus explanations ofthe process will be omitted. When the container 12 is oriented to havethe mouth 11 point downward as in the present embodiment, it is possibleto prevent carbon powder as a by-product generated in forming a carbonfilm from dropping in the container and being attached to the container.Accordingly, air cleaning of the container in the post process can beconsiderably simplified.

As described above, according to the present invention, the voltageapplied to the inner face of the container can be made approximatelyuniform by using the dielectric member installed between the externalelectrode and the container, and the clearance between the externalelectrode and the container or the clearance between the dielectricmember and the container inner face. Therefore, uniform film formationon the entire container can be achieved.

The barrier property can be relatively lower particularly in the case ofa container to be filled with soft drink or the like, for example.Accordingly, by using one tubular electrode of a cylindrical shape,relatively satisfactory film can be formed on various types ofcontainers without changing the type of the electrode. Therefore, in afilm forming system that forms a film on a large quantity of containers,type change for film formation according to various containers isomitted, and thus system efficiency is greatly improved.

A higher barrier property is required for a container to be filled withbeer, for example, and sharing of one tubular electrode of a cylindricalshape cannot achieve a sufficient barrier property. However, when d/∈ isuniformized over the entire container by properly selecting thedielectric member, the clearance thickness, or the relative permittivity∈ according to the present invention, satisfactory film formation can beachieved even for a container of a complicated shape with concaves andconvexes, and thus a barrier property fifteen times higher can be easilyobtained.

When a much higher barrier property is required, it is necessary to usea container without concave and convex. However, also in such cases, thepresent invention can suppress reduction in the barrier property due tothe production accuracy, the molding accuracy, or the installationaccuracy. Accordingly, a much higher barrier property (for example,twenty times higher) can be obtained.

At this time, because the film distribution becomes uniform, the samelevel of coloring is entirely obtained. Therefore, the problem occurringin the conventional techniques of forming a thick film to achieve a highbarrier property, in which the b value is about 4 at a less coloredportion while the b value is 7 to 8 at a more colored portion can beresolved.

Therefore, also in the case of a container to be filled with beer or thelike and requiring high barrier, the b value can be suppressed to equalto or smaller than 4, and thus a container with a pleasing appearancecan be obtained.

Because uniform film formation can be achieved, long film formation timeis not required even when a high barrier property is needed unlike inthe conventional technique, and generation of carbon powder dust can besuppressed correspondingly.

When the container has a concave or convex surface, uniformity in thefilm can be conventionally achieved only by the method of using themicrowave, for example, and providing a low film quality and a lowbarrier property. However, according to the present invention, uniformfilm formation can be obtained by the film forming method using a highfrequency and providing a high barrier property.

The present invention can achieve the above effects all together, andcontributes to great improvement in the container coating technology.

As described above, according to the barrier-film forming apparatus andthe barrier-film forming method of the present invention, uniform filmformation can be achieved in the case in which the size of the clearancebetween the container and the external electrode becomes an issue,particularly for a container including a concave or convex surface.Accordingly, formation of a film with a higher barrier property than inthe conventional techniques can be achieved at low cost.

1-42. (canceled)
 43. A barrier-film forming apparatus that forms abarrier film on an inner face of a container having at least one concaveor convex portion as a processing target container, the barrier-filmforming apparatus comprising: a dielectric member that has a cavitysized to enclose the container; an external electrode that covers anouter circumference of the dielectric member; an exhaust unit that isinstalled on an end face of the external electrode on a side where amouth of the container is located, with an insulating member interposedtherebetween, and depressurizes inside of the container through anexhaust pipe; a gas blowout unit that blows out medium gas forgenerating a barrier film, into the container; and an electric-fieldapplying unit that applies an electric field for generating dischargebetween the external electrode and a ground electrode.
 44. Thebarrier-film forming apparatus according to claim 43, wherein thedielectric member has a tubular shape or an approximately tubular shapewith a bottom or without bottom, and an average thickness/a permittivityof the dielectric member is in a range of 0.95 to 3.8.
 45. Thebarrier-film forming apparatus according to claim 43, wherein a sum ofconverted distances d_(i)/∈_(i) obtained by dividing a thickness (d_(i))of the dielectric member or a space by a relative permittivity (∈_(i))from an inner surface of the external electrode to the inner face of thecontainer is approximately uniform over the entire container.
 46. Thebarrier-film forming apparatus according to claim 43, wherein a materialof the dielectric member, thicknesses of the dielectric member and thespace, and a shape of the external electrode are combined to make a sumof the converted distances d_(i)/∈_(i) from an inner surface of theexternal electrode to the inner face of the container approximatelyuniform over substantially the entire container.
 47. The barrier-filmforming apparatus according to claim 43, wherein, with respect to a sumof converted distances d_(i)/∈_(i) obtained by dividing a thickness(d_(i)) of the dielectric member or a space by a relative permittivity(∈_(i)) at each point of the container surface on a cross section of thecontainer from an inner surface of the external electrode to the innerface of the container, a value obtained by dividing a standard deviationof the sum at each point of the entire container by an average thereofis equal to or lower than 0.75.
 48. A barrier-film forming method ofapproximately uniformly forming a barrier film on an inner face of acontainer as a processing target by using the barrier-film formingapparatus according to claim
 43. 49. A barrier-film forming method ofapproximately uniformly forming a barrier film on an inner face of acontainer as a processing target by using the barrier-film formingapparatus according to claim 43, wherein the container as the processingtarget has an approximately tubular shape.
 50. A barrier-film formingmethod of approximately uniformly forming a barrier film on an innerface of a container as a processing target by using the barrier-filmforming apparatus according to claim 43, wherein the container as theprocessing target has an approximately tubular shape and has at leastone concave portion.
 51. A barrier-film forming method of approximatelyuniformly forming a barrier film on an inner face of a container as aprocessing target by using the barrier-film forming apparatus accordingto claim 43, wherein plural dielectric members having various cavityshapes are prepared, one of the dielectric members is selected to besuited to a shape or the like of the container as the processing target,and the barrier film is then formed on the container.
 52. A barrier-filmforming method of approximately uniformly forming a barrier film on aninner face of a container as a processing target by using thebarrier-film forming apparatus according to claim 43, wherein all or apart of the dielectric member, all or a part of the external electrode,and all or a part of the earth shield are moved together as a unit by adriving unit, and the vacuum container is opened or closed to insert orremove the container.
 53. A barrier-film forming method, wherein thebarrier-film forming apparatus according to claim 43 is used, and thecontainer is inserted or removed by neck handling.
 54. A barrier-filmcoated container that is obtained by approximately uniformly forming abarrier film on an inner face of a container as a processing target byusing the barrier-film forming apparatus according to claim
 43. 55. Abarrier-film forming apparatus comprising: a dielectric member having acavity sized to enclose at least a primary portion of a container as aprocessing target, which cavity matches a space formed by a maximum pathline on which an outer circumference of the container passes, or has aclearance outside the space; an external electrode installed on a sideof an outer circumference of the dielectric member; an exhaust unit thatdepressurizes inside of the container through an exhaust pipe; a gasblowout unit that blows out medium gas for generating a barrier film,into the container; and an electric-field applying unit connected to theexternal electrode to generate discharge in the container, wherein abarrier film is provided on an inner face of the container.
 56. Abarrier-film forming method of approximately uniformly forming a barrierfilm on an inner face of a container as a processing target by using thebarrier-film forming apparatus according to claim
 55. 57. A barrier-filmforming method of approximately uniformly forming a barrier film on aninner face of a container as a processing target by using thebarrier-film forming apparatus according to claim 55, wherein thecontainer as the processing target has an approximately tubular shape.58. A barrier-film forming method of approximately uniformly forming abarrier film on an inner face of a container as a processing target byusing the barrier-film forming apparatus according to claim 55, whereinthe container as the processing target has an approximately tubularshape and has at least one concave portion.
 59. A barrier-film formingmethod of approximately uniformly forming a barrier film on an innerface of a container as a processing target by using the barrier-filmforming apparatus according to claim 55, wherein plural dielectricmembers having various cavity shapes are prepared, one of the dielectricmembers is selected to be suited to a shape or the like of the containeras the processing target, and the barrier film is then formed on thecontainer.
 60. A barrier-film forming method of approximately uniformlyforming a barrier film on an inner face of a container as a processingtarget by using the barrier-film forming apparatus according to claim55, wherein all or a part of the dielectric member, all or a part of theexternal electrode, and all or a part of the earth shield are movedtogether as a unit by a driving unit, and the vacuum container is openedor closed to insert or remove the container.
 61. A barrier-film formingmethod, wherein the barrier-film forming apparatus according to claim 55is used, and the container is inserted or removed by neck handling. 62.The barrier-film forming apparatus according to claim 55, wherein thedielectric member has an opening through which the container can beinserted from a bottom of the container toward a bottom of the externalelectrode of a tubular shape with a bottom.
 63. A barrier-film coatedcontainer that is obtained by approximately uniformly forming a barrierfilm on an inner face of a container as a processing target by using thebarrier-film forming apparatus according to claim
 55. 64. A barrier-filmforming apparatus that forms a barrier film on an inner face of acontainer, wherein voltage to be applied to the inner face of thecontainer is made approximately uniform by using: a dielectric memberinstalled between an external electrode and the container; and aclearance between the external electrode and the container, or aclearance between the dielectric member and the inner face of thecontainer, a mouth end portion of the external electrode points downwardto orient the container to have a mouth pointing downward, and anexhaust pipe is attached below the end portion of the externalelectrode, with an insulating member interposed therebetween, therebyforming the barrier film on the inner face of the container.
 65. Abarrier-film forming method of using the barrier-film forming apparatusaccording to claim 64, wherein the container is vertically inverted, andinsertion or removal of the container into or from the externalelectrode is then performed by neck handling.
 66. A barrier-film coatedcontainer that is obtained by using the barrier-film forming apparatusaccording to claim 64, wherein the container is vertically inverted, andinsertion or removal of the container into or from the externalelectrode is then performed by neck handling, thereby forming a barrierfilm on an inner face of the container as a processing target.
 67. Abarrier-film forming apparatus that forms a barrier film on an innerface of a container having at least one concave or convex portion as aprocessing target container, the barrier-film forming apparatuscomprising: a dielectric member that has a cavity sized to enclose thecontainer; an external electrode that covers an outer circumference ofthe dielectric member; an exhaust unit that is installed on an end faceof the external electrode on a side where a mouth of the container islocated, with an insulating member interposed therebetween, anddepressurizes inside of the container through an exhaust pipe; a gasblowout unit that blows out medium gas for generating a barrier film,into the container; and an electric-field applying unit that applies anelectric field for generating discharge between the external electrodeand a ground electrode, wherein a mouth end portion of the externalelectrode points downward to orient the container to have a mouthpointing downward, and the exhaust pipe is attached below the endportion of the external electrode, with the insulating member interposedtherebetween, thereby forming the barrier film on the inner face of thecontainer.
 68. A barrier-film forming method of using the barrier-filmforming apparatus according to claim 67, wherein the container isvertically inverted, and insertion or removal of the container into orfrom the external electrode is then performed by neck handling.
 69. Abarrier-film coated container that is obtained by using the barrier-filmforming apparatus according to claim 67, wherein the container isvertically inverted, and insertion or removal of the container into orfrom the external electrode is then performed by neck handling, therebyforming a barrier film on an inner face of the container as a processingtarget.
 70. A barrier-film forming apparatus comprising: a dielectricmember having a cavity sized to enclose at least a primary portion of acontainer as a processing target, which cavity matches a space formed bya maximum pass line on which an outer circumference of the containerpasses, or has a clearance outside the space; an external electrodeinstalled on a side of an outer circumference of the dielectric member;an exhaust unit that depressurizes inside of the container through anexhaust pipe; a gas blowout unit that blows out medium gas forgenerating a barrier film, into the container; and an electric-fieldapplying unit connected to the external electrode to generate dischargein the container, wherein a mouth end portion of the external electrodepoints downward to orient the container to have a mouth pointingdownward, and the exhaust pipe is attached below the end portion of theexternal electrode, with an insulating member interposed therebetween,thereby forming a barrier film on an inner face of the container.
 71. Abarrier-film forming method of using the barrier-film forming apparatusaccording to claim 70, wherein the container is vertically inverted, andinsertion or removal of the container into or from the externalelectrode is then performed by neck handling.
 72. A barrier-film coatedcontainer that is obtained by using the barrier-film forming apparatusaccording to claim 70, wherein the container is vertically inverted, andinsertion or removal of the container into or from the externalelectrode is then performed by neck handling, thereby forming a barrierfilm on an inner face of the container as a processing target.